On June 16, 1994, at 0210 eastern daylight time, a Piper PA-31- 350, N4093U, entered a fog bank during the landing flare over runway 36 at the Waterbury-Oxford Airport in Oxford, Connecticut. The pilot elected to do a missed approach and before the airplane started to climb, it landed hard on the runway. The airplane skidded off the runway and down into a ravine. The pilot was not injured. The airplane was substantially damaged. Instrument meteorological conditions prevailed and an Instrument Flight Rules flight plan was filed for the positioning flight. The flight was conducted under 14 CFR Part 91. The pilot stated, "I got down to minimums at the middle marker and had the runway in sight. Over the runway and beginning the flare I flew into a fog bank. I began a missed approach but the next thing I knew I was on the ground. The aircraft began swerving to the right and continued until it was off the runway and down an embankment where it came to rest." Post-accident examination of the accident area revealed three different black rubber deposit marks just beyond the runway's touchdown zone markers. The three black marks continue to the right of the runway centerline until they departed off the runway into grass. Cut marks on the runway were present following along the same path as the right black mark. Markings on the grass continued through the grass and down an embankment and stopped at the airplane. The airplane came to rest in a ravine about 787 feet away from the initial black markings. The main gear were still attached to the airplane but were displaced outward from their normal position. Both main gears' lower link assembly side brace were fractured. Optical examinations of the fracture faces revealed features typical of overstress. The nose gear remained attached to the fuselage but was bent to the left. Post-accident examination of the airframe and engines did not reveal any pre-landing anomalies.